Flash memory bears little resemblance to a magnetic recording system. Commodity flash chips are closed systems with no external access to analog signals, in sharp contrast to the typical Hard Disk Drive (HDD) where analog signals have always been available for study. Even though a HDD is a complex electro-mechanical system and can suffer catastrophic failure, it has been possible to engineer drives to have a life expectancy with little to no degradation in performance, which last beyond their time of technical obsolescence. Flash memory, on the other hand, has a finite life expectancy with gradual degradation in performance through the life cycle. Even so, since flash memory was first conceived as a memory device, the target error rate at the output of the chip has been very low, as opposed to systems where stronger error correction coding (ECC) may be used.
Lower priced solid state drives (SSDs) are typically manufactured using multi-level cell (MLC) flash memory for increased data capacity, but MLC may be less reliable than single-level cell (SLC) flash memory. Consumer SSD manufacturers have mitigated such problems by employing interleaving, special writing algorithms, and/or providing excess capacity in conjunction with wear-leveling algorithms. MLC flash life span (for example, a total number of programming/erase cycles before producing an unacceptable error rate), however, may be sacrificed to meet the requirements of mainstream consumer flash applications, which require flash to have low cost, long retention time, fast programming/erase, and low overall error rate to work with unsophisticated controllers, and, consequently, has not been proven acceptable for many enterprise SSD applications. Even with the increased data capacity of MLC, it may be more expensive to use in enterprise applications because of its disproportionately large reduction in cycle endurance due to increased (wear causing) stresses that are required to read, program, and erase the flash.